1. Field of the Invention
Exemplary embodiments of the present invention relate to a light emitting diode chip and a method of fabricating the same and, more particularly, to a light emitting diode chip having improved luminous efficiency and a method of fabricating the same.
2. Description of the Background
Gallium nitride (GaN)-based blue or ultraviolet (UV) light emitting diodes (LEDs) have been used in a wide range of applications. In particular, various kinds of LED packages for emitting mixed color light, for example, white light, have been applied to backlight units, general lighting, and the like.
Since optical power of the LED package generally depends upon luminous efficiency of an LED chip, numerous studies have focused on development of LED chips having improved luminous efficiency. For example, to improve light extraction efficiency, a rough surface may be formed on a light emitting plane of the LED chip, or the shape of an epitaxial layer or transparent substrate may be adjusted.
Alternatively, a metal reflector such as Al may be disposed on a chip mounting plane opposite to the light emitting plane to reflect light traveling towards the chip mounting plane, which may improve luminous efficiency. Namely, the metal reflector may be used to reflect light and reduce optical loss, improving luminous efficiency. However, reflective metals may suffer from deterioration in reflectivity upon oxidation and the metal reflector may have a relatively low reflectivity.
Accordingly, recent studies have focused on both high reflectivity and relatively stable reflective characteristics of a reflective layer using a laminate of materials having different indices of refraction alternately stacked one above another.
However, such an alternating lamination structure may have high reflectivity in a narrow wavelength band and low reflectivity in other wavelength bands. Accordingly, for an LED package that uses light subjected to wavelength conversion through phosphors or the like to emit white light, the alternating lamination structure may not provide effective reflective characteristics with respect to the light subjected to wavelength conversion and may have limited ability to improve luminous efficiency of the LED package. Further, the alternating lamination structure may exhibit high reflectivity to vertically incident light, but may exhibit relatively low reflectivity to light having a relatively high angle of incidence.
The wavelength band with high reflectivity may be widened by increasing the total number of layers stacked in the alternating lamination structure and adjusting the thickness of each of the layers. However, a large number of layers in the alternating lamination structure may make it difficult to adjust the thickness of each of the layers, and changing the total number of layers may change the thickness of each of the layers, thereby making it difficult to determine an optimal thickness of each of the layers.